The Principal Investigator proposes to continue a prospective epidemiological study of HIV-1-associated CMV retinitis (CMVR). The specific aims of the original research included determining the incidence of resistant CMV, the risk factors for development of resistance, and the relationship between resistance and clinical outcome. This research will expand upon the prior Aims by evaluating plasma CMV DNA viral load as a means of identifying patients who harbor resistant virus, evaluating direct plasma screening for UL97 mutations to identify rapidly patients with ganciclovir-resistant CMV, and comparing ganciclovir resistance mutations between vitreous, blood, and urine samples.